Lawn mover sharpening attachment

ABSTRACT

A sharpening attachment for a grass cutting machine of the rotating cylinder type has an abrasive element which, in use, is pivotally mounted on a tie bar of the machine by two adjustable arms, a spring element interconnecting the two arms and a positioning member in use mounted on said tie bar and acting on the spring element such that the abrasive element is brought into a spring pressured relationship with the blades of the machine so as to sharpen the blades on rotation thereof.

United States Patent [1 1 Riach et a1.

[4 Feb. 18, 1975 1 LAWN MOVER SI-IARPENING ATTACHMENT [75] Inventors: Allan Riach, Ayton; Thomas Sinclair, Eyemouth, both of England [73] Assignee: P. D. Springall Limited, I-Ienlow tlmpa iedfqrd En land [22] Filed: July 11, 1973 [21] Appl. No.: 378,121

[52] US. Cl 51/250, 56/250, 76/821 [51] Int. Cl B24b 3/42 [58] Field of Search 51/250; 56/250; 76/821; 403/93 [56] References Cited UNITED STATES PATENTS 942,578 12/1909 Merritt 51/250 1,164,538 12/1915 Madden 2,118,199 5/1938 Healy 51/250 FOREIGN PATENTS OR APPLICATIONS 448,949 6/1936 Great Britain 51/250 13,877 7/1893 Great Britain 403/93 Primary Examiner-Al Lawrence Smith Assistant ExaminerNicholas P. Godici Attorney, Agent, or Firm-Finnegan, Henderson, Farabow & Garrett [57] ABSTRACT A sharpening attachment for a grass cutting machine of the rotating cylinder type has an abrasive element which, in use, is pivotally mounted on a tie bar of the machine by two adjustable arms, a spring element interconnecting the two arms and a positioning member in use mounted on said tie bar and acting on the spring element such that the abrasive element is brought into a spring pressured relationship with the blades of the machine so as to sharpen the blades on rotation thereof.

5 Claims, 5 Drawing Figures FIG].

PATENTED FEB 8 I975 SHEET 1 or 3 LAWN MOVER SHARPENING ATTACHMENT FIELD OF THE INVENTION This invention relates to a sharpening attachment for a grass cutting machine of the rotating cylinder type and to grass cutting machines including such an attachment.

SUMMARY OF THE PRIOR ART Previous proposals have suggested a sharpening attachment having an abrading element disposed in a complicated frame that is detachably pivoted at each end by several nut and bolt fixtures upon a projection which has to be fixed to the grass cutting machine. It has also been suggested that the frame might have an adjustable means for moving the abrading element relative to the blades of the cutter see for example British Pat. No. 336,025. Another form of sharpening attachment is disclosed in British Pat. No. 220,001 in which the sharpening is effected by two whet stones that are held against the blade by spring blades however such a device is not removable and is unsuitable for application on rotating cylinder cutting machines.

An advantage of the present invention is its simplicity of construction and the convenient manner in which it may be easily located on the tie bar of a grass cutting machine.

SUMMARY OF THE INVENTION According to the present invention a sharpening attachment for a grass cutting machine comprises an abrasive element adapted for removable connection to a tie bar on a machine in a position such that when in use the abrasive element is adapted to be disposed so as to sharpen the blades of a machine on rotation of the blades.

According to a further feature of the invention a sharpening attachment for a grass cutting machine comprises an abrasive element, two arms secured to the abrasive element, means on each arm adapted for pivotal engagement with a tie bar on the machine, positioning means adapted for connection to the tie bar of the machine and spring means associated with the positioning means such that the abrasive element can be held in a desired spring-biased position adjacent the blades of the machine.

The invention also includes a sharpening attachment for a grass cutting machine comprising an abrasive element mounted in an elongate frame, two arms securedto, and extending away from, each of the arms at the end remote from the frame being adapted for pivotal connection to a tie bar on the machine, a spring element interconnecting the two arms and means, adapted to be adjustably disposed upon the tie bar intermediate the two arms, for holding the spring element in a desired disposition such that in use the abrasive element may be brought into spring-pressured relationship with the blades of a machine.

Another feature of the invention includes a grass cutting chi a in ms q p osed i m mbers interconnected by a tie bar, a plurality of blades rotatably mounted between the side members and a sharpening attachment removably connected to the machine said attachment comprising an abrasive element removably connected to the tie bar and a spring element associated with the abrasive element such that the abrasive element is held in a position against the blades so as to sharpen the blades of the machine on rotation of the blades.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described by way of example with reference to the accompanying drawings in which:

FIG. I is a partially schematic front view of one embodiment of the invention;

FIG. 2 is a side view of the same embodiment in the direction of arrow A of FIG. 1;

FIG. 3 is a side view of an arm used in a second embodiment of the invention;

FIG. 4 is a sectional view on the line 4-4 of FIG. I; and

FIG. 5 is a front perspective view of a third embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the drawings a sharpening attachment 1 for attachment to a grass cutting machine generally indicated 2 comprises a sheet of abrasive material 3 disposed in the front face of an elongated moulded polyvinyl chloride frame 4. Intermediate the ends of the frame 4 and extending away from the back face of the frame 4 are two members 5 and 6 to which arms 7 and 8 respectively are adjustably secured at 9. Arms 7 and 8 have a substantially elongate body portion 10 with a hooked end 11 joined by way of a shoulder portion 12. Disposed within the shoulder portion 12 is a hole 13 which forms a fixture point for a spring element 14 which interconnects the two arms 7 and 8.

Forming an operative, but separate, part of the attachment 1 is a positioning member 15 clearly shown in FIG. 4. The member 15 is in the form of an L-shaped arm having a short limb 16 and a long limb 17. The member 15 is conveniently releasably secured to a tie bar 18 on the machine 2 by a worm drive hose clip 19 that is tightened over and about the limb 16. The limb 17 is substantially rectangular in shape except for a notch 20 formed in one side edge, the member 15 being disposed in a position such that the notch 20 may be brought into contact with the spring element 14.

The two embodiments of the invention as illustrated in FIGS. 2 and 3 respectively differ mainly in the construction of the adjustable means 9 and the hooked end 11. In the first embodiment the member 5 or 6 comprises two aligned substantially triangular members 21 separated by the arm 7 or 8. In each corner of the members 21 is a hole 22, two of these holes 22 in each member 21 forming the means of attachment to the back of the frame 4. The members 5 or 6 are disposed in slots in the back of the frame such that the latter-mentioned holes 22 are aligned with tubes 23 and 24 formed integral on the back of frame 4. The members 5 or 6 are then attached to the frame 4 by passing suitable metal strengthening rods through the tubes 23 and 24 and also through the holes 22.

The arm 7 or 8 is movable about a pivot 25 disposed in the exposed holes 22 of the members 21. The arm 7 or 8 is then locked in a desired position by means of a fluted arcuate end surface 26 the circumference of which passes through one of holes 22 aligned with tubes 23 and 24. The size of the flutings on the surface 26 corresponds to the size of the holes 22 and therefore it is locked in the desired position when the rods are passed through the tubes 23 and 24 to secure the members and 6 as seen in dotted lines in FIG. 2. The hooked end 11 of the arms 7 and 8 in the first embodiment are substantially planar as shown.

In the second embodiment the members 5 and 6 are secured to the frame 4 in a similar manner but the adjustable locking means is not associated therewith. In this embodiment members 5 and 6 comprise one part only having two holes 22 where they are secured to the frame 4 and a circle of eight holes formed at its other end. The members 5 and 6 are pivotally secured to respective arms 7 and 8 by a pivot such as pin 27 passing through the centre of the circle of holes and also through the centre of a second, communicating circle of nine holes 28 formed in the arms 7 and 8. The arms 7 and 8 are therefore angularly adjustable relative to members 5 and 6, the vernier principle of the communicating holes allowing relative movement in multiples of 5, by moving the arms about the pin 28 to a desired position and then locking the respective members and arms together by a suitable stop 29 where a hole in each of the two circles coincide. The hooked end 11 in this second embodiment functions in the same manner as the first embodiment but is provided with a much broader hook. However, if desired the hook may be planar as in the first embodiment.

In operation the sheet of abrasive material 3 is disposed in the frame 4 by sliding it between frame flanges 30 and members 5 and 6 are secured to the back of the frame 4 by passing suitable rods through tubes 23 and 24; the adjustable means 9 of the first embodiment being suitably arranged before passing the rods through tubes 23 and 24. In the case of the second embodiment arms 7 and 8 are then secured by adjustment in the desired position as described above. The spring element 14 is then passed between shoulder portions 12 to interconnect the arms 7 and 8. To place the attachment on a grass cutting machine the hooks of the arms 7 and 8 are placed over a tie bar on the machine so that the attachment swings freely. The attachment is then brought into spring-pressured contact with the blades of the machine by adjusting the member to force and hold the spring element 14 in a direction towards the blades of the machine. The only part of the attachment that need remain on the machine is the member 15 secured to the tie bar, the rest of the attachment may be removed and replaced as desired without any securing nuts having to be released.

In the third embodiment as shown in FIG. 5 the attachment is disposed in front of the blades of the machine. Owing to this particular arrangement it is advantageous to make the spring element 14 of a different configuration to that illustrated with reference to the first and second embodiments to ensure that the abrasive element is correctly biased against the blades of the machine.

In this embodiment a tie bar 18 is disposed in front of the rotatable blades of a machine 2. All parts of the attachment excepting the spring element 14 are preferably of the same construction as described with reference to the two previous embodiments. However, this embodiment uses a spring element 14 that is stepped at both ends, i.e., both ends of the spring element lie outside the arms 7 and 8 and are substantially perpendicu- 6 respective holes 13 in parts 7 and 8. The advantage of this particular arrangement is that in use the part 15 urges the central portion of the spring element 14 towards the blades of the machine which has the reaction offorcing the ends of the spring element into the tie bar thus ensuring that the arms 7 and 8 maintain their position on the tie bar. We have found that this modification of the spring element 14 helps prevent the possibility of vibration jarring the arms 7 and 8 from the tie bar.

Although this spring element has been particularly described for use when the attachment is disposed in front of the blades it is understood that it may also be used when the attachment is disposed behind the blades.

In the situation where a machine has no tie bar one would have to be suitably secured as a permanent fix ture. The attachment is made of any suitable material but preferably the frame is an extruded polyvinyl chloride plastics material and the arms are made of a metal or plastics material.

The abrasive element may be a sheet or a block of e.g., carborundum (silicon carbide) or fused aluminium oxide and may be secured to a frame in any suitable manner.

In the first embodiment as it is necessary to remove the rods to be able to adjust the angle of the arms it may be preferable to provide heads to one end of the rods that protrude from one end of the frame so that the rods may be removed and replaced as desired.

We claim:

1. A grass cutting machine having a frame of two opposed side members interconnected by a tie bar, a plurality of blades rotatably mounted between the side members and a sharpening attachment removably connected to the machine, said attachment comprising (a) an elongated frame, (b) an abrasive element carried by said frame, (c) said frame being removably connected to the tie bar, (d) a plurality of arms secured to the back face of the frame and extending away from the frame, each arm comprising a fixed part secured to the frame and an adjustable part angularly adjustable relative to the fixed part, (e) spring means interconnecting two of the adjustable parts, (f) means on each adjustable part for providing pivotal engagement on the tie bar, and (g) positioning means adjustable disposed on the tie bar intermediate the two adjustable parts for holding the spring means in a desired disposition such that in use the abrasive element, by suitable angular relationship of the arms, is brought into spring biased relationship with the blades of the machine.

2. In a sharpening attachment for a grass cutting machine of the rotating cylinder type having opposed side members interconnected by a tie bar and a plurality of blades rotatably mounted between the side members comprising an elongated frame, an abrasive element carried by said frame, and means for releasably securing the frame to the tie bar in a position such that the abrasive element is disposed to sharpen the blades of the machine upon rotation of the blades, that improvement which includes a. a plurality of arms secured to the back face of the frame and extending away from the frame,

each arm comprising a fixed part secured to the frame and an adjustable part angularly adjustable relative to the fixed part,

b. spring means interconnecting two of the adjustable parts, c. means on each adjustable part for providing pivotal engagement on the tie bar, and d. positioning means adjustably disposed on the tie bar intermediate the two adjustable parts for holding the spring means in a desired disposition such that in use the abrasive element, by suitable angular relationship of the arms, is brought into spring biased relationship with the blades of the machine. 3. A sharpening attachment according to claim 2 wherein the adjustable part of each arm has a fluted arcuate surface at the end adjacent the fixed part and the fixed part of each arm has a portion positioned to seat in a predetermined arcuate portion of said surface whereby said parts are located in a particular angular relationship.

4. A sharpening attachment according to claim 2 wherein the angular adjustment between fixed and adjustable parts comprises a pivot about which both parts may rotate, the fixed part having a circle of holes centered on said pivot, and the adjustable part having another circle of holes centered on said pivot of radius equal to the first mentioned circle but differing in number of holes, the holes being arranged to receive a fastening member.

5. A sharpening attachment according to claim 2 wherein the positioning means comprises an L-shaped member formed with a notch in its longer limb the member being adapted to be secured to a tie bar of a machine by a worm drive hose clip and movable about the tie bar such that the notch may be brought into contact with the spring element. 

1. A grass cutting machine having a frame of two opposed side members interconnected by a tie bar, a plurality of blades rotatably mounted between the side members and a sharpening attachment removably connected to the machine, said attachment comprising (a) an elongated frame, (b) an abrasive element carried by said frame, (c) said frame being removably connected to the tie bar, (d) a plurality of arms secured to the back face of the frame and extending away from the frame, each arm comprising a fixed part secured to the frame and an adjustable part angularly adjustable relative to the fixed part, (e) spring means interconnecting two of the adjustable parts, (f) means on each adjustable part for providing pivotal engagement on the tie bar, and (g) positioning means adjustable disposed on the tie bar intermediate the two adjustable parts for holding the spring means in a desired disposition such that in use the abrasive element, by suitable angular relationship of the arms, is brought into spring biased relationship with the blades of the machine.
 2. In a sharpening attachment for a grass cutting machine of the rotating cylinder type having opposed side members interconnected by a tie bar and a plurality of blades rotatably mounted between the side members comprising an elongated frame, an abrasive element carried by said frame, and means for releasably securing the frame to the tie bar in a position such that the abrasive element is disposed to sharpen the blades of the machine upon rotation of the blades, that improvement which includes a. a plurality of arms secured to the back face of the frame and extending away from the frame, each arm comprising a fixed part secured to the frame and an adjustable part angularly adjustable relative to the fixed part, b. spring means interconnecting two of the adjustable parts, c. means on each adjustable part for providing pivotal engagement on the tie bar, and d. positioning means adjustably disposed on the tie bar intermediate the two adjustable parts for holding the spring means in a desired disposition such that in use the abrasive element, by suitable angular relationship of the arms, is brought into spring biased relationship with the blades of the machine.
 3. A sharpening attachment according to claim 2 wherein the adjustable part of each arm has a fluted arcuate surface at the end adjacent the fixed part and the fixed part of each arm has a portion positioned to seat in a predetermined arcuate portion of said surface whereby said parts are located in a particular angular relationship.
 4. A sharpening attachment according to claim 2 wherein the angular adjustment between fixed and adjustable parts comprises a pivot about which both parts may rotate, the fixed part having a circle of holes centered on said pivot, and the adjustable part having another circle of holes centered on said pivot of radius equal to the first mentioned circle but differing in number of holes, the holes being arranged to receive a fastening member.
 5. A sharpening attachment according to claim 2 wherein the positioning means comprises an L-shaped member formed with a notch in its longer limb the member being adapted to be secured to a tie bar of a machine by a worm drive hose clip and movable about the tie bar such that the notch may be brought into contact with the spring element. 